PATTERNS OF CHARACTER DIVERGENCE AND THE EVOLUTION OF REPRODUCTIVE ECOTYPES OF DALECHAMPIA SCANDENS (EUPHORBIACEAE)

The variation of four floral characters (resin-gland area, gland-stigma distance, gland-anther distance, and anther-stigma distance) was analyzed across 15 populations of Dalechampia scandens occurring sympatrically, in various combinations, with five other congeners. Univariate and multivariate analysis of variance and a posteriori comparison tests indicate that there are significant statistical patterns of character divergence away from sympatric congeners for three of the floral characters. These characters, which on the basis of common garden studies appear to be under genetic control, may not vary independently; i.e., genetic control may be overlapping. The characters appear to be functionally related. Populations of Dalechampia scandens occurring sympatrically with congeners possessing relatively large resin glands, large gland-stigma distances and large anther-stigma distances (e.g., D. dioscoreifolia and D. affinis) have significantly smaller resin glands, gland-stigma distances and anther-stigma distances than do populations occurring sympatrically with congeners with relatively small resin glands, gland-stigma distances, and anther-stigma distances (e.g., D. cissifolia, D. heteromorpha and D. schottii). Populations of D. scandens not sympatric with other Dalechampia species generally have intermediately sized structures. The pattern of bidirectional divergence is consistent with the evolutionary scenario that selection against interspecific pollination has resulted in local ecotypic differentiation and character displacement in populations sympatric with ecologically similar congeners.     

COMPARATIVE ANATOMY OF THE PETIOLE AND INFRAGENERIC RELATIONSHIPS IN JATROPHA (EUPHORBIACEAE)

Anatomical features of the petiole in several species of Jatropha L. (Euphorbiaceae) are presented as evidence in support of infrageneric relationships. A trilacunar 3-trace nodal pattern is typical for the genus. The vascular supply to the stipules is derived from the branching of the two peripheral leaf traces. The number of vascular bundles range from 11 through 9, 7, 5 and 3, and occur in a ring, as free traces, a medullated cylinder, or as U-shaped free traces. The reduction from nine to three bundles is correlated with the gross morphological features while 11, which occurs only in the section Peltatae (Pax) Dehgan & Webster, presents an increase. Reduction in the number of petiolar traces follows the evolutionary advancement of various taxa. This reduction in traces corresponds with south-north distribution of the species and consequential adaptation to colder and more arid climates in Central America and Africa. Smaller leaves, fewer primary veins and fewer vascular traces have resulted as a response to reduced need for water. Presence of dorsal (super-numerary) bundles which supply the petiolar glands in subgenus Jatropha (= Adenoropium Pax) is considered significant, since African taxa of the section (subsection Pubescentes Pax) have retained these bundles despite the loss of petiolar glands. The latter glands are prominent in the South American and Indian species. Sectional lines in the genus can, therefore, be drawn generally on the basis of numerical constancy and relative uniformity in the arrangement of petiolar traces. The continuity of vascular bundles from the stem into the petiole and variations of bundle arrangements are depicted in three-dimensional drawings.     

POLLINATION OF DALECHAMPIA MAGNOLIIFOLIA (EUPHORBIACEAE) BY MALE EUGLOSSINE BEES

Flowers of Dalechampia magnoliifolia in eastern Peru were pollinated primarily by male Eulaema meriana and E. cingulata, which collected fragrance from the secretory gland borne in the staminate cymule. The fragrance contains carvone oxide, benzyl acetate, limonene, α-pinene, myrcine, β-pinene/camphene, and carvone. Trigona cf. pallens was the most abundant visitor, but was primarily a pollen thief. The rate of contact with the stigmas by Trigona, and hence the bee's efficacy as a pollinator, was highly variable and was determined by variation in the separation of anthers and stigmas. Dalechampia magnoliifolia co-occurred with a congeneric species, D. cissifolia, but did not share pollinators with it.     

THE MORPHOLOGY AND RELATIONSHIPS OF BARBEYA OLEOIDES

Barbeya, a monotypic genus of dioecious, arborescent dicotyledonous plants from northeast Africa and adjacent Arabia, is usually regarded as having affinities within the Urticales. It is placed either in the Ulmaceae or segregated as a closely related, monotypic family. Leaves are opposite, exstipulate, and vascularized by a single, crescent-shaped trace from a unilacunar node. Wood anatomy indicates specialization at about the same level as other Urticales. Sieve tube elements of the secondary phloem exhibit highly oblique, compound sieve plates which indicate a low level of evolutionary advancement. The vascularity of the flower is described and compared with other Urticales. Pollen is tricolporate. The relationships of the genus to Moraceae, Ulmaceae, Urticaceae, and Eucommiaceae are discussed. The totality of anatomical and morphological evidence supports the retention of the family Barbeyaceae.     

SEED PRODUCTION AND DISPERSAL IN DALECHAMPIA (EUPHORBIACEAE): DIVERGENT PATTERNS AND ECOLOGICAL CONSEQUENCES

Patterns of capsule development and methods of seed dispersal are described and compared for 16 neotropical species of Dalechampia. In 15 species all the capsules in a single inflorescence develop simultaneously. In one species, D. spathulata, the capsules develop sequentially. I suggest that the difference between D. spathulata and the other species is the result of the fact that D. spathulata occurs in a low-light, rainforest environment, whereas the other species grow in high-light environments. Sequential development of capsules appears to reduce the loss of seeds to seed predators in species that occur in light-limited environments. The seeds of all 16 species of Dalechampia are dispersed by explosive dehiscence of the capsules. Within the genus there are several different adaptations that increase the average dispersal distance for the seed crop.     

FLORAL PAEDOMORPHY LEADS TO SECONDARY SPECIALIZATION IN POLLINATION OF MADAGASCAR DALECHAMPIA (EUPHORBIACEAE)

The traditional evolutionary interpretation of Von Baer's “laws” of embryology is that retention of early developmental forms into adulthood (paedomorphosis) leads to the evolution of simpler or more generalized morphology and ecology. Here we show that paedomorphosis can also be involved in an increase in ecological specialization, in this case of plant–pollinator relationships. A paedomorphic transition from generalized pollination (by several functional types of pollinators) to specialized pollination (by one or a few species in one functional type) occurred in a clade of endemic Madagascar vines (Dalechampia spp., Euphorbiaceae). This evolutionary transition involved staminate flowers that fail to develop “normally,” instead holding mature pollen inside virtually unopened, bud‐like flowers. This paedomorphic morphology restricts reward access to “buzz‐pollinating” bees, including Xylocopa species (carpenter bees), which can remove pollen by sonication. This is one of very few reports of paedomorphic specialization, and, as far as we are aware, the first documented case of a rapid reversal to specialized pollination in a lineage of plants that had previously switched from specialized to generalized pollination in conjunction with dispersing to a new region.     

POLLINATION OF TWO SYMPATRIC SPECIES OF DALECHAMPIA (EUPHORBIACEAE) IN SURINAME BY MALE EUGLOSSINE BEES

Dalechampia brownsbergensis and D. fragrans co-occur in Suriname, and both are pollinated by fragrance-collecting male euglossine bees. Dalechampia brownsbergensis appears to bloom year-round and is pollinated by relatively few species of bees, including Euglossa tridentata and E. gaianii. In contrast, D. fragrans appears to bloom from late October through early December and is visited and pollinated by at least 13 species of euglossines. Field observations of pollination indicated that the two species did not share pollinators. However, when the flowers of D. fragrans were “transplanted” into a population of D. brownsbergensis, the main pollinator of D. brownsbergensis also visited the flowers of D. fragrans. The pollinators of D. fragrans, however, did not visit the flowers of D. brownsbergensis. Partial sharing of pollinators may have only a small negative impact on the two sympatric plant species at this site because they flower simultaneously only part of the year, and they are often spatially separated from one another.     

MORPHOLOGY,FINE STRUCTURE AND ONTOGENY OF THE STINGING EMERGENCE OF TRAGIA RAMOSA AND T. SAXICOLA (EUPHORBIACEAE)

The ontogeny and ultrastructure of Tragia ramosa and T. saxicola are described. The stinging emergence of T. ramosa and T. saxicola consists of a central stinging cell and three lateral cells. The stinging cell possesses a compound crystal in the apical region which is held in place by cell wall extensions. The stinging cell cytoplasm is characterized by a large central vacuole which contains a proteinaceous substance as determined histochemically. Upon contact, the stinging cell wall is pushed back over the crystal, exposing it to penetrate an individual. This stinging mechanism is unique among stinging emergences. The stinging cell is subepidermal in origin whereas the three lateral cells are epidermal in origin. The morphology, ultrastructure and ontogeny of the stinging emergence of T. ramosa and T. saxicola appear to be identical.     

POLLINATION ECOLOGY OF FOUR DALECHAMPIA SPECIES (EUPHORBIACEAE) IN NORTHERN NATAL,SOUTH AFRICA

The pollination ecology of four Dalechampia species was studied in three areas in northern Natal, South Africa. All species were pollinated by resin- and/or pollen-collecting megachilid bees (Hymenoptera: Megachilidae). The most common of these at all study sites was Heriades sp. (Megachilini), which collected both pollen and resin. This bee was the primary pollinator of D. galpinii and D. volubilis, and a secondary pollinator of D. aff. parvifolia and D. capensis. The primary pollinators of these latter two Dalechampia were Pachyanthidium near cucullatum and P. cordatum (Anthididiini), respectively. These are larger bees that collected mainly resin. Other visitors varied among Dalechampia species and among sites. Pairs of Dalechampia species were often found in sympatry (within 30 m of each other) and shared pollinators to varying extents. “Transfer experiments,” in which we placed inflorescences of two Dalechampia species together, reinforced observations of flower discrimination by bees foraging among naturally occurring sympatric pairs. Heriades sp. showed no obvious discrimination between Dalechampia species, but Pachyanthidium spp. “preferred” the Dalechampia species with the greater resin reward. Occasionally, however, Pachyanthidium would visit less rewarding species. Thus, although sympatric African Dalechampia species showed some pollinator partitioning, it was much weaker than found among New World species, and cannot alone explain the general absence of Dalechampia hybrids in northern Natal.     

POLLEN MORPHOLOGY,TRICHOME TYPES,AND RELATIONSHIPS OF THE GRONOVIOIDEAE (LOASACEAE)

The pollen of all four genera of Gronovioideae—Cevallia, Fuertesia, Gronovia, and Petalonyx—was examined in light microscopy, and scanning and transmission electron microscopy. The pollen of Cevallia, of Fuertesia, and of Gronovia can be easily distinguished from each other and from all remaining Loasaceae. Only Petalonyx, with a striate tectum, shows a clear relationship to the Mentzelioideae and Loasoideae, the vast majority of which have striate-reticulate or striate tecta. The trichome data are mostly congruent with the pollen data: Cevallia, Fuertesia, and Gronovia each have a distinctive trichome not known to occur elsewhere in the family, while Petalonyx has only the common types. A cladistic analysis of Gronovioideae utilizing Mentzelia as the outgroup proposes that Cevallia, Gronovia, and Fuertesia are a sister group to Petalonyx within the subfamily. The relationships of the four genera to each other and of Gronovioideae to the Loasaceae are discussed.     

THE COMPARATIVE MORPHOLOGY AND RELATIONSHIPS OF THE MAGNOLIACEAE. III. CARPELS

Canright , James E. (Indiana U., Bloomington.) The comparative morphology and relationships of the Magnoliaceae. III. Carpels. Amer. Jour. Bot. 47(2): 145—155. Illus. 1960.–The morphology and vascular anatomy of the carpels of 49 species in 9 of the 10 genera of the Magnoliaceae are described. Assuming that the conduplicate carpel of Australasian species of Drimys (Winteraceae) represents the primitive condition, various carpellary modifications are indicated for the Magnoliaceae. These evolutionary spcializations from the basic type include: basal adnation, lateral concrescence, reduction in number of ovules, closure of the ventral suture, and localization of stigmatic areas. Among the examined species it was determined that carpels of the genera Elmerrillia and Manglietia retain the most primitive features, whereas those of the genus Liriodendron possess the most advanced. Comparisons are made with the gynoecia of related ranalean families, viz., Himantandraceae, Degeneriaceae and Annonaceae.     

POLLEN MORPHOLOGY AND THE RELATIONSHIPS OF SIMMONDSIA CHINENSIS TO THE ORDER EUPHORBIALES

Pollen from Simmondsia chinensis (Simmondsiaceae) was examined in LM, SEM, and TEM. The pollen is shed as monads, triangular in shape in polar view, with a 3-porate aperture type in which the pores are large and poorly defined. The tectum is irregularly scabrate, sometimes forming minute “islands” topped with spinules. In thin section, the endexine is thickened and lamellate in the aperture regions, and narrow in the mesoporus; the foot layer is well-defined but noticeably thicker in the mesoporus; and thin columellae support an essentially complete tectum. The pollen of four genera, Buxus, Pachysandra, Sarcococca, and Styloceras, from the Buxaceae to which Simmondsia has been assigned by some authors, was also examined and illustrated. The pollen morphology of two families frequently aligned with Simmondsiaceae, Euphorbiaceae and Pandaceae, is briefly discussed. For the most part pollen morphology supports the treatment of Simmondsia as a monotypic family, Simmondsiaceae.     

POLLEN MORPHOLOGY AND THE RELATIONSHIPS OF CIRCAEASTER,OF KINGDONIA,AND OF SARGENTODOXA TO THE RANUNCULALES

The pollen of three monotypic genera, Circaeaster, Kingdonia, and Sargentodoxa has been examined by light and scanning electron microscopy and in the case of the last genus, also by transmission electron microscopy. The type of tectum found in Circaeaster and Kingdonia, derivations of a compound layer of striae, has a restricted distribution in the Order Ranunculales. Of 64 genera examined in this order only six had species with a similar tectum. They include Achlys, Epimedium, Jeffersonia, and Vancouveria of the Berberidaceae s.l., the controversial Hydrastis, and Trollius of the Ranunculaceae. Circaeaster and Kingdonia have been considered as related since both have rare and primitive vegetative characteristics, the most notable being open dichotomous leaf venation. They are probably best treated as a ditypic family, Circaeasteraceae. The pollen of Sargentodoxa, especially the structure of the exine, closely resembles that of the Lardizabalaceae. However, the fruits of Sargentodoxa have been considered to be distinct from those of the Lardizabalaceae, suggesting that it be treated as a separate, but closely allied, family.     

THE MORPHOLOGY AND RELATIONSHIPS OF RHODEA,TELANGIUM, TELANGIOPSIS,AND HETERANGIUM

This study deals with four form or organ genera from the Upper Mississippian (Chester Series) of the Illinois Basin, and provides evidence that they were produced by a single natural genus with gymnospermous affinity. The plant remains—compressions, impressions, petrifactions, and specimens that combine compression or impression with petrifaction—allow examination of both external morphology and internal anatomy. The specimens include foliage corresponding to Rhodea, stems and petioles corresponding to Heterangium, and synangiate fructifications corresponding to either Telangium or Telangiopsis. The stems and foliage are considered parts of the same plant because of the identity of the anatomical and cuticular features of petioles attached to stem and those petioles with attached foliage. The fertile material is regarded as part of the same plant because: (1) The anatomy of axes of the fertile specimens is like that of the sterile specimens. (2) A single specimen may contain both sterile Rhodea-type axes and fertile regions. (3) Axes bearing synangia have the same size and patterns of divisions as the sterile foliage. Features that indicate lyginopterid affinities include: (1) Equal forking of the petiole. (2) Presence of fiber bands in the outer cortex and sclerotic nests in the inner part of the cortex. (3) Crowded circular bordered pits on the lateral walls of the metaxylem tracheids. (4) The presence of a small amount of secondary xylem. A variety of structural details of the stem and petiole suggest the genus Heterangium. The phyletic position of the plant that produced Rhodea, Telangium, Telangiopsis, and Heterangium is reviewed in light of such discoveries as the presence of a planated frond that lacks a lamina and the presence of both monolete and trilete microspores in a single synangium.     

KLEINODENDRON AND XYLEM ANATOMY OF CLUYTIEAE (EUPHORBIACEAE)

Kleinodendron, a new genus of Euphorbiaceae, was assigned by Smith and Downs to the tribe Cluytieae. A xylem anatomical survey indicates that there are no objections to this placement. Woods of Cluytieae are diverse but may be characterized generally by having pores which average less than 80 μ in diameter and which are well divided between solitary and radial multiple distributions in the same species; simple vessel perforations; alternate intervascular pitting; fiber-tracheids and libriform wood fibers; exclusively uniseriate, or uniseriate and biseriate heterocellular vascular rays in the same species; uniseriate “bridges” linking superposed biseriate ray segments; diffuse, diffuse-in-aggregates, and scanty vasicentric axial parenchyma, sometimes in the same species; and crystal rhomboids. That Microdesmis and Pogonophora diverge sharply from these generalizations in having scalariform vessel perforations and broad vascular rays, is an indication that they may not be closely related to other genera in Cluytieae.     

THE ORIGIN AND RELATIONSHIPS OF LASTHENIA BURKEI (COMPOSITAE)

Lasthenia burkei (Compositae) is a narrowly restricted California endemic closely related to L. conjugens and L. fremontii. These three species differ from each other by pappus and phyllary characters and in geographical distribution. All are freely intercrossable, but L. fremontii forms rather sterile artificial hybrids with its two relatives which, in turn, form fairly fertile artificial hybrids with each other. Lasthenia burkei and L. conjugens have homologous chromosomes, four of which are homologous with four of those of L. fremontii. The remaining two chromosomes probably have reciprocal translocations which lead to multivalent formation during meiosis in interspecific hybrids. Pollen viability is restored in most F₂ generations, suggesting a close genetic relationship among the three species. The evolutionary relationship among these species may be a linear one with L. burkei occupying an intermediate position between L. fremontii and L. conjugens, although the direction of this linear phylogeny is not certain, or it may be one in which L. burkei has been derived from hybridization between its two relatives. Support for the latter hypothesis comes from the appearance of some individuals in F₁ progenies of L. conjugens × L. fremontii that are morphologically indistinguishable from L. burkei (although fairly sterile). The apparently rather simple genetic basis for the morphological characteristics of each of the species in this trio suggests that the morphologically heterogeneous genus Lasthenia may be considerably more homogeneous genetically than might be suspected. Because of the diverse kinds of relationships among these three Lasthenias, possible alternative taxonomies for the group are dependent upon those relationships that a taxonomist wishes to communicate. Nevertheless, the patterns of diversification in this group have led to reaffirmation of an earlier decision that three species should be recognized.     

POLLEN MORPHOLOGY AND THE RELATIONSHIPS OF AËTOXYLON,AMYXA, AND GONYSTYLUS TO THE THYMELAEACEAE

The pollen of three closely related genera, Aëtoxylon, Amyxa, and Gonystylus is compared in SEM and TEM with that of Thymelaeaceae, s. s. The Thymelaeaceae have spherical, pantoporate grains with a crotonoid tectum in which the basic subunit is triangular in shape and forms a continuous triangular array. Thin section (TEM) and fractures (SEM) revealed that these subunits are attached to a ringlike network of horizontal rods. Within the Thymelaeaceae, the triangular subunits vary in the number of subdivisions and degree of fusion and form a morphological continuum. Aëtoxylon, Amyxa, and Gonystylus also have spherical, pantoporate pollen but with a tectum in which almost all of the distinction of the subunits appears to have been lost. The structure of the exine in Aëtoxylon, Amyxa, and Gonystylus, however, is unique thus far within the angiosperms. Thin section revealed a thick tectum with a layer of short or even granular columellae, then a thin, discontinuous layer from which larger columellae appear to hang. There is no evidence of an endexine even in the region of the apertures. The distinctive exine structure would support the treatment of Aëtoxylon, Amyxa, and Gonystylus as a separate family, Gonystylaceae, allied to the Thymelaeaceae.     

几种枝角类的卵鞍形态及表面超微结构

用光镜和扫描电镜对浙东地区八种常见淡水枝角类卵鞍形态和表面结构进行了观察和比较。卵鞍形态多为三角形或豆荚形,表面大都具特定的纹饰,内储冬卵1－2枚。卵鞍的形态、表面纹饰、冬卵的数量的排列方向具有种的特异性。枝角类的分类地位相距越远,卵鞍形态和表面结构相差越大,相近种和亚种间的卵鞍在光镜下难以区别,亚显微结构却有一定的差异。卵鞍的形态和结构作为枝角类的分类依据是有意义的。